Centrifugal turbomachine with two stages arranged back-to-back and with an annular transfer duct between the stages

ABSTRACT

The turbomachine assembly includes a first turbomachine having an inlet, an outlet and a rotary shaft, a second turbomachine having an inlet, an outlet and a rotary shaft, a transfer duct fluidly connecting the outlet of the first turbomachine to the inlet of the second turbomachine, and a casing housing the turbomachines and the transfer duct; the turbomachines are located adjacent to each other so that the outlet of the second turbomachine is close to the outlet of the first turbomachine and the inlet of the second turbomachine is remote from the outlet of the first turbomachine; the outlet of the second turbomachine has an end portion shaped like a cochlea (i.e. a spiral duct); the transfer duct has an annular shape, and surrounds the end portion of the outlet of the second turbomachine.

BACKGROUND

Embodiments of the subject matter disclosed herein correspond to turbomachine assemblies, transfer ducts for connecting turbomachines, and methods of arranging ducts.

In the field of “Oil & Gas”, it is common to fluidly connect two or more turbomachines in cascade.

This is the case, for example, when a fluid needs to be compressed at high compression ratio: instead of using a single (and very long) multistage compressor, two (shorter) multistage compressors are used and connected in cascade, as shown in FIG. 1.

FIG. 1 shows, by way of example, a turbomachine assembly 100 comprising a first multistage centrifugal compressor 110, a second multistage centrifugal compressor 120 and an electric motor (not shown in the figure); all the machines of the assembly 100 are housed inside a hermetic casing 130. The assembly 100 is intended for subsea installation. The first compressor 110 has an inlet 111 (on the left side in the figure), an outlet 112 (on the right side in the figure) and a rotary shaft 113 (protruding for example on both sides in the figure). The second compressor 120 has an inlet 121 (on the right side in the figure), an outlet 122 (on the left side in the figure) and a rotary shaft 123 (protruding for example on both sides in the figure); the shafts 113 and 123 are (substantially) coaxial and mechanically coupled together (often a unique solid shaft is used).

A configuration such as the one shown in FIG. 1 is called “back-to-back” as the two machines face in opposite directions. In particular, in FIG. 1, the compressors 110 and 120 are located adjacent to each other and the outlet 112 of the first compressor 110 faces the outlet 122 of the second compressor 120 and is close to it; the outlet 112 of the first compressor 110 and the inlet 121 of the second compressor 120 are fluidly connected but they are remote from each other.

The “back-to-back” configuration is advantageous as, during operation of the assembly, the axial thrust exerted by one of the two machines may be (substantially) balanced by the axial thrust of the other one of the two machines and does not load axially the bearings of the machines; the “back-to-back” configuration is even more advantageous when magnetic bearings are used for supporting the two machines as magnetic bearings can not withstand high axial thrust.

In a turbomachine assembly with “back-to-back” configuration, the fluid connection between the first and second machines requires a long piping as the outlet of the first machine and the inlet of the second machine are remote from each other.

In the exemplary assembly of FIG. 1, cascade connection of the two compressors 110 and 120 is realized through a transfer piping 140 that is totally external to the casing 130. Piping 140 consists of a shaped pipe 141 with a first flange 142 (on the left in the figure) and a second flange 143 (on the right in the figure) at its two ends. The assembly 100 comprises: a main inlet pipe 131 with a flange 132, a main outlet pipe 133 with a flange 134, an intermediate inlet pipe 135 with a flange 136 and an intermediate outlet pipe 137 with a flange 138; all these pipes protrude from casing 130. Inlet pipe 131 is fluidly connected to inlet 111 (see arrow in the figure), outlet pipe 133 is fluidly connected to outlet 122 (see arrow in the figure), inlet pipe 135 is fluidly connected to inlet 121 (see arrow in the figure), outlet pipe 137 is fluidly connected to outlet 112 (see arrow in the figure). Flange 138 is mechanically connected to flange 142 and flange 136 is mechanically connected to flange 143 so that the outlet of the first compressor 110 is fluidly connected to the inlet of the second compressor 120.

An external transfer piping like the one of FIG. 1 may create problems especially (but not only) when the assembly is placed deep in the sea; there may be leakage from the mechanical connections at its two ends, there may be damages due to collisions and/or erosions and its repairing requires disconnecting and connecting flanges. Furthermore, there may be cooling by the sea water of the working fluid that flows inside it and the working efficiency of the assembly is influenced by such cooling.

SUMMARY

Therefore, there is a general need for improved solutions to the problem of fluidly connecting turbomachines arranged in “back-to-back” configuration, especially for subsea applications in the field of “Oil & Gas”.

More in general, there is a need for improved solutions to the problem of arranging distinct and separate ducts in the same space.

An important idea is to locate the transfer duct inside the casing.

Another important idea is to shape the transfer duct as an annular duct.

Another important idea is to provide one pipe-shape seat inside the transfer duct.

Another important idea is to provide one or more struts inside the transfer duct.

First embodiments of the subject matter disclosed herein relate to turbomachines assembly.

In the general, the turbomachine assembly comprises:

a first turbomachine having an inlet, an outlet and a rotary shaft,

a second turbomachine having an inlet, an outlet and a rotary shaft,

a transfer duct fluidly connecting the outlet of the first turbomachine to the inlet of the second turbomachine, and

a casing housing the turbomachines and the transfer duct;

the turbomachines are located adjacent to each other so that the outlet of the second turbomachine is close to the outlet of the first turbomachine and the inlet of the second turbomachine is remote from the outlet of the first turbomachine; the outlet of the second turbomachine has an end portion shaped like a cochlea; the transfer duct has an annular shape, and surrounds the end portion of the outlet of the second turbomachine.

Second embodiments of the subject matter disclosed herein relate to transfer ducts for fluidly connecting the outlet of a first turbomachine to the inlet of a second turbomachine.

In general, the transfer duct consists of a single duct; the single duct has an annular shape around an axis; the single duct develops at the begin at least partially radially, in the middle substantially axially and at the end at least partially radially; the single duct has one pipe-shaped seat for housing at least partially another duct crossing it; the single duct has one or more struts for structural reinforcement.

Third embodiments of the subject matter disclosed herein relate to methods of arranging a first and a second distinct and separate ducts, the first duct being designed for feeding a first fluid in an axial direction and the second duct being designed for feeding a second fluid in a radial direction.

In general, the method comprises:

configuring the first duct as a single annular duct so to define an internal space,

configuring the second duct as a single spiral duct,

positioning the second duct inside the internal space defined by the first duct,

prolonging the single spiral duct so to cross the single annular duct.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate exemplary embodiments of the present invention and, together with the detailed description, explain these embodiments. In the drawings:

FIG. 1 is a schematic view of a longitudinal cross-section of a turbomachine assembly according to the prior art,

FIG. 2 is a schematic view of a longitudinal cross-section of a turbomachine assembly according to an embodiment of the present invention,

FIG. 3 is a partial enlarged detailed view of FIG. 2 and regards a transfer duct,

FIG. 4 shows a partial longitudinal cross-sectional detailed view of an embodiment of a turbomachine assembly according to an embodiment of the present invention, and

FIG. 5 shows a partial transversal cross-section view corresponding to the embodiment of FIG. 4.

DETAILED DESCRIPTION

The following description of exemplary embodiments refers to the accompanying drawings.

The following description does not limit the invention. Instead, the scope of the invention is defined by the appended claims.

Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

FIG. 2 is a schematic view of a longitudinal cross-section of a turbomachine assembly 200; it comprises:

a first turbomachine 210 having an inlet 211, an outlet 212 and a rotary shaft 213 (with axis 214),

a second turbomachine 220 having an inlet 221, an outlet 222 and a rotary shaft 223 (with axis 224),

-   -   a transfer duct 240 fluidly connecting the outlet 212 to the         inlet 221, and

a casing 230 housing turbomachines 210 and 220 and transfer duct 240.

The turbomachines 210 and 220 are located adjacent to each other so that the outlet 222 of the second turbomachine 220 is close to the outlet 212 of the first turbomachine 210 and the inlet 221 of the second turbomachine 220 is remote from the outlet 212 of the first turbomachine 210; in particular, they are in the so-called “back-to-back configuration”. According to this embodiment, shafts 213 and 223 are exactly coaxial and a single axis 204 corresponds to both axis 214 of shaft 213 and axis 224 of shaft 223. According to this embodiment, shafts 213 and 223 are mechanically coupled together through a rigid joint (not highlighted in the figure); alternatively, for example, a unique solid shaft may be used.

The outlet 222 of the second turbomachine 220 has an end portion 225 shaped like a cochlea (i.e. a spiral duct).

The transfer duct 240 is a single duct with an annular shape (both internally and externally) and surrounds the end portion 225 of the outlet 222 of the second turbomachine 220; in particular, the transfer duct 240 surrounds axially and radially (i.e. completely) not only portion 225 but the whole second turbomachine 220 (only small zones close to the shaft 223 of the second turbomachine 220 are not surrounded—see right side and left side in FIG. 2).

The transfer duct 240 is completely internal to the casing 230.

The transfer duct 240 develops at the begin 241 at least partially radially (getting far from its axis 204, i.e. increasing its distance) and in the middle 242 substantially axially and at the end 243 at least partially radially (getting close to its axis 204, i.e. decreasing its distance)—see FIG. 3 wherein the transfer duct 240 (with its longitudinal axis 204 of symmetry) of FIG. 2 is partially shown in cross-section and in enlarged scale. The transfer duct 240 has a first end portion, at the begin 241, directly fluidly connected to the outlet 212 of the first turbomachine 210 (for example “outlet diffuser”) and a second end portion, at the end 243, directly fluidly connected to the inlet 221 of the second turbomachine 220 (for example “inlet guider”). At the begin 241, the area of the cross-section of the transfer duct 240 increases (i.e. the transfer duct widens); this is shown in FIG. 2 and is even more clear in FIG. 4.

As it is clear from FIG. 2, the transfer duct 240 develops as a mantle around the second turbomachine 220 starting at the outlet 222 of the second turbomachine 220 (actually a bit before) and ending at the inlet 221 of the second turbomachine 220 (actually a bit after).

Assembly 200 has one inlet duct, in the form of a pipe 231 with a flange 232, and one outlet duct, in the form of a pipe 233 with a flange 234; both ducts, i.e. pipes 231 and 233, protrude from the casing 230.

The end portion 225 of the outlet 222 of the second turbomachine 220 is fluidly connected to the outlet duct 233 of the assembly through a connection duct 235. The connection duct 235 passes through the transfer duct 240; more specifically, it goes from one side, i.e. the internal wall, to the other side, i.e. the external wall, of the transfer duct 240. The connection duct 235 is a prolongation of the cochlea 225 and is partially housed in a pipe-shaped seat of the transfer duct 240 (see also FIG. 5); the transfer duct 240 may have one or more elements (for example connecting its internal wall and its external wall) for structural reinforcement.

FIG. 4 and FIG. 5 should be considered together as they show detailed views of a possible embodiment; they embody technical solutions similar to those described with reference to the schematic views of FIG. 2 and FIG. 3.

FIG. 4 highlights a transfer duct (in the form of a single annular duct) that develops at the begin 441 at least partially radially (in an outward direction, i.e. far from the shafts and their axes), in the middle 442 substantially axially and at the end 443 at least partially radially (in an inward direction, i.e. close to the shafts and their axes). The end portion of the transfer duct at the begin 441 is directly fluidly connected to a duct 412 (for example a “outlet diffuser”) that may be considered an outlet of a first turbomachine; the end portion of the transfer duct at the end 443 is directly fluidly connected to a duct 421 (for example a “inlet guider”) that may be considered an inlet of a second turbomachine. The transfer duct is completely internal to the casing and surrounds the second turbomachine completely in the radial direction and almost completely in the axial direction (only small zones close to the shaft of the second turbomachine are not surrounded).

The radial distance between the transfer duct and the axis of the shaft of the second machine increases along the begin 441 of the transfer duct; this allows to overcome the second turbomachine.

The area of the cross-section of the transfer duct increases along the begin 441 of the transfer duct (in other words, the transfer duct widens); this allows to reduce the speed (especially its axial component) of the fluid flowing inside the transfer duct and consequently to recover some pressure; in other words, the initial portion of the transfer duct acts similarly to an outlet cochlea of a turbomachine.

FIG. 4 highlights also an end portion 425 of an outlet of the second turbomachine (corresponding to end portion 225 of FIG. 2) that is shaped like a cochlea; portion 525 may be connected, for example, to an “outlet diffuser” of the second turbomachine.

The portion of the transfer duct at the begin 441 surrounds the end portion 425 of the outlet of the second turbomachine completely in the radial direction and completely, only on one side, in the axial direction.

FIG. 5 highlights a transfer duct 540 in the form of a single annular duct (around an axis 504); this allows to gradually reduce (to an angle in the range e.g. of 10°-30°) the rotational component of the speed of the fluid flowing inside the transfer duct. The figure seems to show two semi-annular cavities separated by elements 544 and 545; indeed, the annular cavity is only one as elements 544 and 545 have a limited axial extension. The external side or wall of transfer duct 540 is adjacent or very close to the casing of the assembly while the internal side or wall of the transfer duct 540 is adjacent to an end portion 525 of the outlet of a second turbomachine (corresponding to end portion 225 of FIG. 2) that is shaped like a cochlea; portion 525 leaves a central space 501 free.

Portion 525 is to be fluidly connected to an outlet duct of the assembly; this is the purpose of connection duct 535 (corresponding to duct 235 of FIG. 2).

Connection duct 535 passes through transfer duct 540; more specifically, it goes from one side, i.e. the internal wall, to the other side, i.e. the external wall, of the transfer duct 540. Connection duct 535 is a prolongation of the cochlea-shape duct 525. Transfer duct 540 has one pipe-shaped seat 544 housing partially (or totally) connection duct 535 crossing it.

Transfer duct 540 has one strut 545 (or more than one, for example two or three or four or five or six or seven or . . . ) for structural reinforcement; such structural element is a (relatively) short solid element that may be arranged radially or substantially radially.

Heat insulating material (for example in the form of layers) may be place between the transfer duct and the cochlea-shape duct and/or between connection duct and transfer duct.

FIG. 4 and FIG. 5 have allowed to describe and show in detail a possible configuration and a possible arrangement of a transfer duct according to the embodiments of the present invention.

As it is clear for a person skilled in the art from the above description, a first and a second distinct and separate ducts have been arranged; the first duct is designed for feeding a first fluid in an axial direction and the second duct is designed for feeding a second fluid in a radial direction.

According to such arrangement, the following steps are provided:

configuring the first duct as a single annular duct so to define an internal space,

configuring the second duct as a single spiral duct,

positioning the second duct inside the internal space defined by the first duct, and

prolonging the single spiral duct so to cross the single annular duct.

Such arrangement is particularly effective when the first and second fluid flows come from outlets of turbomachines; in fact, it allows to minimize load losses and/or heat losses and/or heat exchanges.

From the application point of view, the embodiments of the present invention are very flexible.

According to a specific embodiment (in “back-to-back configuration”), the first and second turbomachines mentioned before may be for example compressors or pumps, multistage centrifugal machines (the number of stages of the first machine may be equal to or different from the number of stages of the second machine); but the assembly may comprise further machines, for example an engine such as an electric motor or a turbine; especially when an electric motor is used, the compressors or pumps are fluidly well isolated from the engine.

According to another specific embodiment (in “back-to-back configuration”), the first turbomachine is a compressor or pump, a multistage centrifugal machine, the second turbomachine is a turbine, a multistage machine.

All the machines of the assembly are housed inside the same casing.

In general, the rotary shafts of these machines are mechanically coupled together; in FIG. 2, shaft 213 of machine 210 and shaft 223 of machine 220 are mechanically coupled together through a rigid joint (a unique solid shaft is an alternative).

In an embodiment of the present invention is in turbomachine assemblies designed to be installed subsea.

This written description uses examples to disclose the invention, including the preferred embodiments, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

1. A turbomachine assembly comprising: a first turbomachinc having an inlet, an outlet and a rotary shaft, a second turbomachine having an inlet, an outlet and a rotary shaft, a transfer duct fluidly connecting the outlet of the first turbomachine to the inlet of the second turbomachine, and a casing housing the first turbomachine and the second turbomachine and the transfer duct; wherein the first turbomachine and the second turbomachine are located adjacent to each other so that the outlet of the second turbomachine is close to the outlet of the first turbomachine and the inlet of the second turbomachine is remote from the outlet of the first turbomachine; wherein the outlet of the second turbomachine has an end portion shaped like a cochlea; and wherein the transfer duct has an annular shape, and surrounds the end portion of the outlet of the second turbomachine.
 2. The turbomachine assembly of claim 1, wherein the transfer duct develops at the beginning at least partially radially and/or in the middle substantially axially and/or at the end at least partially radially.
 3. The turbomachine assembly of claim 1, wherein the transfer duct develops as a mantle around the second turbomachine starting at the outlet of the second turbomachine and ending at the inlet of the second turbomachine.
 4. The turbomachine assembly of claim 1, further comprising an outlet duct protruding from the casing; wherein the end portion of the outlet of the second turbomachine is fluidly connected to the outlet duct of the assembly through a connection duct; and wherein the connection duct passes through the transfer duct.
 5. The turbomachine assembly of claim 1, wherein the transfer duct surrounds completely the second turbomachine.
 6. The turbomachine assembly of claim 1, wherein the transfer duct comprises: a first end portion directly fluidly connected to the outlet of the first turbomachine, and a second end portion directly fluidly connected to the inlet of the second turbomachine.
 7. The turbomachine assembly of claim 6, wherein the area of the cross-section of the transfer duct increases along the first end portion.
 8. The turbomachine assembly of claim 6, wherein the distance between the transfer duct and an axis the shaft of the second machine increases along the first end portion.
 9. The turbomachine assembly of claim 1, wherein the first turbomachine is a first compressor or first pump: wherein the second turbomachine is a second compressor or second pump;and wherein the rotary shafts of the first turbomachine and the second turbomachine are mechanically coupled together.
 10. The turbomachine assembly of claim 1, wherein the first turbomachine is a compressor or pump; wherein the second turbomachine is a turbine; and wherein the rotary shafts of the first turbomachine and the second turbomachine are mechanically coupled together.
 11. The turbomachine assembly of claim 1, being for subsea installation.
 12. A transfer duct, the transfer duct comprising: a single duct, whereine the transfer duct is for fluidly connecting an outlet of a first turbomachine to an inlet of a second turbomachine wherein the single duct has an annular shape around an axis; wherein the single duct develops at the beginning at least partially radially, in the middle substantially axially and at the end at least partially radially; wherein the single duct has one pipe-shaped seat for housing at least partially another duct crossing it; and wherein the single duct has preferably one or more struts or structural reinforcement.
 13. A method of arranging a first and a second distinct and separate ducts, the first duct being designed for feeding a first fluid in an axial direction and the second duct being designed for feeding a second fluid in a radial direction; comprising: providing the first duct configured to be as a single annular duct so to define an internal space, providing the second duct configured to be as a single spiral duct, positioning the second duct inside the internal space defined by the first duct, and prolonging the single spiral duct so to cross the single annular duct.
 14. The transfer duct of claim 12, wherein the transfer duct develops as a mantle around the second turbomachine starting at the outlet of the second turbomachine and ending at the inlet of the second turbomachine.
 15. The transfer duct of claim 12, futher comprising an outlet duct; wherein the end portion of the outlet of the second turbomachine is fluidly connected to the outlet duct of the assembly through a connection duct; and wherein the connection duct passes through the transfer duct.
 16. The transfer duct of claim 12, wherein the transfer duct surrounds completely the second turbomachine
 17. The transfer duct of claim 12, wherein the transfer duct further comprises: a first end portion directly fluidly connected to the outlet of the first turbomachine, and a second end portion directly fluidly connected to the inlet of the second turbomachine.
 18. The transfer duct of claim 12, wherein the first turbomachine is a first compressor or pump; wherein the second turbomachine is a second compressor, pump or turbine; and wherein the rotary shafts of the first turbomachine and the second turbomachine are mechanically coupled together.
 19. The turbomachine assembly of claim 9, wherein the first turbomachine is a multistage centrifugal machine and the second turbomachine is a multistage centrifugal machine.
 20. The turbomachine assembly of claim 10, wherein the first turbomachine is a multistage centrifugal machine and the second turbomachine is a multistage machine. 